Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/calibration/documentation/epic_cal_meetings/200502/mst_bkgtool.pdf Дата изменения: Fri May 16 13:32:26 2014 Дата индексирования: Wed Apr 13 13:23:48 2016 Кодировка: Поисковые слова: магнитосфера земли

A new SAS background task

XMM
1


Why a SAS background task?
· Point sources in FF modes: Source and background regions could be well defined. Background subtraction possible. · MOS SW mode: No background region in central CCD, but in peripheric CCDs. Background subtraction possible. · PN SW: Could be very difficult to define background region. For very bright sources no background in SW area. · Extended sources: If diameter of the source > FOV definition of background region impossible. background model needed.

XMM-Newton
Martin Stuhlinger, ESAC 2


Examples

XMM-Newton
Martin Stuhlinger, ESAC 3


Working scheme for PN FF/MOS
· Get particle+electronic background from out-FOV regions. (Sufficient statistics for short observations?) Scale particle background region to user defined background region. Subtract particle bkg from user defined bkg to get photon background. Correct photon background for vignetting effects. Add corrected photon bkg and particle bkg to total background. Scale total background to the user defined source region.

· · · · ·

Implementation as SAS task.

XMM-Newton
Martin Stuhlinger, ESAC 4


PN SW / Extended sources
· No out-FOV area: Template for particle background needed. · Investigate rules when local background is available: - Source brightness: Possible count rate limit. - Position of the source inside the small window area. · No local background available: background template needed. - Template for particle background. "Background button" - Template for photon background.

XMM-Newton
Martin Stuhlinger, ESAC 5


Problems of background templates
· Templates could be extracted using XMM data archive. · Background is a composite of various components: ­ Electronic noise, proton flares, cosmic particles, CCD fluorescence, cosmic photon background · Each component can show different spectral, temporal and spatial variability (see results of former background workshops). Good understanding of each background component is needed to understand how successful these templates can be used and how these templates can be used successfully.

XMM-Newton
Martin Stuhlinger, ESAC 6